罗非鱼副产物抗菌肽的制备及其对无乳链球菌抑菌活性分析

Preparation of antibacterial peptides from tilapia by-products and analysis of their antibacterial activity against Streptococcus agalactiae

以罗非鱼副产物为原料,采用酸性蛋白酶进行酶解制备抗菌肽,以期提高罗非鱼副产物的利用率和附加值。以对无乳链球菌抑菌效果为指标,通过单因素及正交试验获得最佳酶解工艺条件。测定酶解产物的最小抑菌浓度(minimum inhibit concentration,MIC)以评价其抑菌效果,并采用高效体积排阻色谱(high-performance size-exclusion chromatography,HPSEC)法分离酶解产物,获得肽段分子质量分布图。通过对冻干粉蛋白氨基酸组成分析,探索氨基酸组成与抑菌活性的关系及其作为水产动物饲料添加成分的可行性。结果表明,最佳酶解条件为:酶解时间5 h,酶解温度40℃,pH 2.0,料液比1∶5(g∶mL),酶添加量为0.7%,对无乳链球菌的抑菌圈直径为23.38 mm,MIC达到12.5μg/μL,说明可以通过酶解方法得到对无乳链球菌具有较好抑菌效果的抗菌肽产品。经最优条件酶解后的罗非鱼副产物粗肽分子质量有68.08%分布在3000 Da以下。氨基酸分析表明,酶解物中与抑菌活性相关的氨基酸含量较高并具有均衡的氨基酸组成,初步表明罗非鱼副产物酶解肽具有较强的营养和功能潜力,为罗非鱼副产物的高值化利用提供了新途径。

In order to expand the usages of tilapia by-products,acid protease was adopted to hydrolyze tilapia by-products to prepare antibacterial peptides.The optimum conditions of enzymatic hydrolysis were obtained by single factor and orthogonal experiments by the index of the antibacterial effect to Streptococcus agalactiae.The minimum inhibitory concentration(MIC)of the enzymatic hydrolysate was tested to confirm its effectiveness,and the hydrolysate was separated by high-performance size-exclusion chromatography(HPSEC)to show its molecular weight distribution.The amino acid composition of the enzymatic hydrolysate was assayed to explore the relationship between composition and antibacterial activity and its feasibility as an additional component to aquatic animal feed.The results showed that the optimum conditions of enzymatic hydrolysis were 40℃,hydrolyzing for 5 h with the enzyme dosage of 0.7%,pH 2.0,and solid-liquid ratio of 1∶5(g∶mL).The diameter of the inhibition zone against Streptococcus agalactiae was 23.38 mm.The MIC value against S.agalactiae was 12.5μg/μL.Under optimal conditions,the molecular weight of the crude peptides of tilapia by-products was 68.08%distributed below 3000 Da.The preliminary results indicate that the hydrolysates of tilapia by-products have strong nutritional and functional potential,which provides a new pathway for the high-value utilization of tilapia by-products.